Costs and benefits of eradicating alien invasive vegetation from the upper reaches of the Mhlatuze catchment.

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Alien invasive vegetation threatens the functioning of natural ecosystems as well as their services, which sustain human welfare, both directly and indirectly. The proliferation of this vegetation in South Africa has been attributed to the ignorance of the social implications affiliated to their existence. Investment decisions are predominantly based on the marginal private costs of an activity, since individuals have not been made accountable for costs imposed on society in the past. Consequently, their marginal private costs always fall well short of the marginal social costs. In order to promote sustainable development as well as curtail widespread invasion by alien plants in South Africa, it is essential to close the gap between these costs and support research aimed at ascertaining monetary values for non-market goods, such as biodiversity. This study scrutinizes the economic viability of alien plant eradication in the Mhlatuze Catchment by comparing the costs and benefits associated with this eradication process. A series of formal in-depth interviews with major stakeholders residing in the upper reaches of the catchment were conducted in an attempt to evoke individuals' perceptions concerning alien vegetation together with the actual costs incurred in extirpating this vegetation. The contingent valuation method (CVM), which relies on surveys to elicit the maximum amount respondents would be willing to pay to obtain or retain some nonmarket good, was employed to glean monetary values for benefits such as biodiversity and augmented streamflow. The findings suggest that there is a positive net effect associated with alien vegetation extirpation in the Mhlatuze Catchment, since the social benefits outweigh the costs. Given the temporal and financial constraints that prevailed, it was only possible to examine some of the benefits affiliated to this process, such as increased timber harvesting, streamflow, biodiversity and reduced fire hazard. Consequently, this analysis represents a minimum estimate of the benefits, further enhancing the argument in favour of extirpation. The results lend support to calls for greater policy emphasis on, as well as funds for, the eradication of alien invasive plants.